2X Barlow:  Use during visual observing to double the magnification of every 1.25” eyepiece you own
Prime Focus Photography: Use the T-Adapter portion of this accessory to transform your telescope into a giant telephoto lens
Tele-Extended Photography:  Use the T-Adapter with Barlow to get double the magnification of prime focus mode 
T-threads accept camera brand specific T-Ring (sold separately)